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WP 5 Ultra-Broadband Technology The novel business scenarios developed within the project, which are partly required and always supported by the new open platform, cause a wide range of service quality parameter values to be fulfilled by the serving platform. In order to serve for any kind of eWork and eCommerce, these requirements (e.g. data volume throughput, data integrity, data delay, data security) are expected to vary over a wide range, which is not known in currently available wireless systems. An highly flexible data transmission scheme is required to cover this extended range still keeping an efficient resource usage. It is believed, that ultra-broadband radio has the potential to serve for this. The work package ultra-broadband technology will provide an Air Interface definition and an advanced physical layer transceiver architecture, which is able to adapt to very different business service requirements instantaneously (on-the-fly) only by the exchange of parameters. As the ultra-broadband technology has been used in the U.S. and Russia for military applications the basic principles of this technology have been proven. In whyless.com these basic principles will be assessed and further developed to be used in the new open mobile radio access network. Two different approaches are used for UWB communication, a carrier free or impulsive UWB system and a spectrally filtered UWB system. They have different advantages and disadvantages as shortly explained below and will both be considered as possible candidates for the air interface of the open mobile access network. General characteristics of UWB systems
Carrier-free UWB In the carrier-free UWB approach the baseband pulse is directly fed to the antenna as shown in the figure below.
In carrier-free UWB systems the information can either be transmitted using on/off keying or pulse positioning modulation (PPM). Generally, a large number of pulses is used to transmit one information symbol. At the receiver, the pulses are coherently combined resulting a high system gain. Instead of transmitting pulses in regular intervals, the pulse positions can be varied defined by a user specific positioning code. The advantage of such dithering is that the transmitted signal looks like noise in the spectral domain and, hence, interference of other systems in the same frequency band is reduced to a minimum. Furthermore, different codes can be used to separate users similar to the access scheme of conventional CDMA systems. The user specific pulse train and the frequency spectrum of a single pulse (monocycle) is given below.
Characteristics of Carrier-free UWB
Spectrally filtered UWB In the spectrally filtered UWB system approach a block of pulse shaped carrier cycles are bandpass filtered and then transmitted to the antenna. This method allows a precise control of the radiated spectrum. With a suitable choice of oscillator and mixer, UWB signal can be generated with center frequencies in between near DC to several GHz. Information can be transmitted using amplitude, pulse position, phase or frequency modulation. Multi-user separation can be done by frequency or by time hopping codes like in the above approach.
Characteristics of spectrally-filtered UWB
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